The number 21939
21939 is a composite number with 8 divisors. Its prime factorisation is 3 × 71 × 103. Divisors (8): 1, 3, 71, 103, 213, 309, 7313, 21939.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21939: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
21939 is composite. Its prime factorisation is
- 3
The divisors add up to 29952; without 21939 itself that is 8013, so 21939 is deficient (8013 is less than 21939). Euler's totient φ(21939) = 14280 numbers up to 21939 share no factor with it.
- 4
The digits of 21939 add up to 24, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 43 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21939 = 3 \times 71 \times 103 \]
21939 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 29952 |
| Euler totient φ(n) | 14280 |
| Square | 481319721 |
| Cube | 10559673359019 |
| Square root | 148.118196 |
| Digit sum / digital root | 24 / 6 |
| Collatz steps to 1 | 43 |
| Scientific notation | 2.1939 × |
21939 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand nine hundred and thirty-nine |
| Binary (base 2) | 101010110110011 |
| Octal (base 8) | 52663 |
| Hexadecimal (base 16) | 55B3 |
| Base 3 | 1010002120 |
| As time | 21939 seconds = 6 h 5 min 39 s |
Is 21939 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21939 ÷ 3 = 7313) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7. |
| 8 | No (remainder 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 5) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 3) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21939 a prime number?
No. 21939 = 3 × 71 × 103, so it is divisible by 3.
What are the factors of 21939?
1, 3, 71, 103, 213, 309, 7313, 21939.
What is 21939 in binary?
101010110110011 (hexadecimal 55B3, octal 52663).
What is the square root of 21939?
About 148.1182.
Is 21939 divisible by 3?
Yes. Its digits add up to 24, a multiple of 3.
What is special about the number 21939?
21939 is a happy number: repeatedly adding the squares of its digits reaches 1.